131 lines
3.8 KiB
Zig
131 lines
3.8 KiB
Zig
// Ported from go, which is licensed under a BSD-3 license.
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// https://golang.org/LICENSE
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//
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// https://golang.org/src/math/sin.go
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const builtin = @import("builtin");
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const std = @import("../std.zig");
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const math = std.math;
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const expect = std.testing.expect;
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/// Returns the sine of the radian value x.
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///
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/// Special Cases:
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/// - sin(+-0) = +-0
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/// - sin(+-inf) = nan
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/// - sin(nan) = nan
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pub fn sin(x: var) @typeOf(x) {
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const T = @typeOf(x);
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return switch (T) {
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f32 => sin_(T, x),
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f64 => sin_(T, x),
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else => @compileError("sin not implemented for " ++ @typeName(T)),
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};
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}
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// sin polynomial coefficients
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const S0 = 1.58962301576546568060E-10;
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const S1 = -2.50507477628578072866E-8;
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const S2 = 2.75573136213857245213E-6;
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const S3 = -1.98412698295895385996E-4;
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const S4 = 8.33333333332211858878E-3;
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const S5 = -1.66666666666666307295E-1;
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// cos polynomial coeffiecients
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const C0 = -1.13585365213876817300E-11;
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const C1 = 2.08757008419747316778E-9;
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const C2 = -2.75573141792967388112E-7;
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const C3 = 2.48015872888517045348E-5;
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const C4 = -1.38888888888730564116E-3;
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const C5 = 4.16666666666665929218E-2;
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const pi4a = 7.85398125648498535156e-1;
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const pi4b = 3.77489470793079817668E-8;
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const pi4c = 2.69515142907905952645E-15;
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const m4pi = 1.273239544735162542821171882678754627704620361328125;
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fn sin_(comptime T: type, x_: T) T {
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const I = @IntType(true, T.bit_count);
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var x = x_;
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if (x == 0 or math.isNan(x)) {
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return x;
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}
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if (math.isInf(x)) {
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return math.nan(T);
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}
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var sign = x < 0;
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x = math.fabs(x);
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var y = math.floor(x * m4pi);
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var j = @floatToInt(I, y);
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if (j & 1 == 1) {
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j += 1;
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y += 1;
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}
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j &= 7;
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if (j > 3) {
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j -= 4;
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sign = !sign;
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}
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const z = ((x - y * pi4a) - y * pi4b) - y * pi4c;
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const w = z * z;
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const r = if (j == 1 or j == 2)
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1.0 - 0.5 * w + w * w * (C5 + w * (C4 + w * (C3 + w * (C2 + w * (C1 + w * C0)))))
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else
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z + z * w * (S5 + w * (S4 + w * (S3 + w * (S2 + w * (S1 + w * S0)))));
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return if (sign) -r else r;
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}
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test "math.sin" {
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expect(sin(f32(0.0)) == sin_(f32, 0.0));
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expect(sin(f64(0.0)) == sin_(f64, 0.0));
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expect(comptime (math.sin(f64(2))) == math.sin(f64(2)));
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}
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test "math.sin32" {
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const epsilon = 0.000001;
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expect(math.approxEq(f32, sin_(f32, 0.0), 0.0, epsilon));
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expect(math.approxEq(f32, sin_(f32, 0.2), 0.198669, epsilon));
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expect(math.approxEq(f32, sin_(f32, 0.8923), 0.778517, epsilon));
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expect(math.approxEq(f32, sin_(f32, 1.5), 0.997495, epsilon));
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expect(math.approxEq(f32, sin_(f32, -1.5), -0.997495, epsilon));
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expect(math.approxEq(f32, sin_(f32, 37.45), -0.246544, epsilon));
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expect(math.approxEq(f32, sin_(f32, 89.123), 0.916166, epsilon));
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}
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test "math.sin64" {
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const epsilon = 0.000001;
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expect(math.approxEq(f64, sin_(f64, 0.0), 0.0, epsilon));
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expect(math.approxEq(f64, sin_(f64, 0.2), 0.198669, epsilon));
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expect(math.approxEq(f64, sin_(f64, 0.8923), 0.778517, epsilon));
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expect(math.approxEq(f64, sin_(f64, 1.5), 0.997495, epsilon));
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expect(math.approxEq(f64, sin_(f64, -1.5), -0.997495, epsilon));
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expect(math.approxEq(f64, sin_(f64, 37.45), -0.246543, epsilon));
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expect(math.approxEq(f64, sin_(f64, 89.123), 0.916166, epsilon));
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}
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test "math.sin32.special" {
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expect(sin_(f32, 0.0) == 0.0);
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expect(sin_(f32, -0.0) == -0.0);
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expect(math.isNan(sin_(f32, math.inf(f32))));
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expect(math.isNan(sin_(f32, -math.inf(f32))));
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expect(math.isNan(sin_(f32, math.nan(f32))));
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}
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test "math.sin64.special" {
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expect(sin_(f64, 0.0) == 0.0);
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expect(sin_(f64, -0.0) == -0.0);
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expect(math.isNan(sin_(f64, math.inf(f64))));
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expect(math.isNan(sin_(f64, -math.inf(f64))));
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expect(math.isNan(sin_(f64, math.nan(f64))));
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}
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